Combined measurement of surface properties of particles and equilibrium parameters of cation exchange from a single kinetic experiment

Abstract

For the Coulombic force adsorption in cation exchange, equilibrium parameters were closely related to the surface properties of particles in aqueous solution. Taking into account the difference in the polarization of two cation species involved in the exchange by introducing a modification coefficient for describing the relatively effective charges of the cation species, the new approaches for estimating exchange equilibrium parameters and surface properties of particles have been developed. Our theory indicates that, just relying on two parameters, the slope and intercept of the first-order rate equation of cation adsorption, the following equilibrium parameters and important surface properties of particles can be obtained easily: (1) surface potential, (2) specific surface area, (3) charge density, (4) electrostatic field strength at the surface, (5) selectivity coefficient, (6) activity coefficients of cation species in the adsorption phase, (7) adsorption quantity of each cation species at equilibrium with strong and weak force adsorption. For the first time, by the quantitative relationship between the selectivity coefficient and surface potential of particles together with polarizability and charge, the number of cation species is established. The results show the difference in the polarizability between two cation species involved in the exchange strongly influences the cation exchange equilibrium and surface properties of particles.